Nano-bubbles have several unique properties such as long lifetime in liquid due to their negatively charged surfaces. Nano-bubbles also have high gas solubility into the liquid due to their high internal pressure. Conversely, micro- and macro-bubbles are larger in size, and thus rise rapidly and burst at the water surface.
Nano-bubbles are applicable in variety of fields and can have numerous beneficial effects from a medical, industrial and agricultural point of view. For example, the presence of nano-bubbles can promote a physiological activity in creatures and increase metabolism, as a result of which ontogenetic growth is enhanced.
To date several methods of generating nano-bubbles have been proposed. These methods include swirl-type liquid flow, venturi, high-pressure dissolution, ejector, mixed vapor direct contact condensation and supersonic vibration. All of these methods are energy intensive and have varying degrees of success in creating nano-bubbles.